SF, I think the key word in your response is "scary". If that is all you are worried about, two is fine, but if you want to play matchups with the average guys as well, its not.
I can say this, I see no problem keeping three for August, the young guys can come back in September (where Matt BETTER be agressive in matchups since he will have a crowded pen) and let the rest of the season say who you carry into the playoffs.
Hell, you get to reset before each series in the playoffs, so you can determine out of the guys that are 7, 8, 9 talent wise, who pitches in that series based on the other line up.
In essence, Thornton, Barrett, Treinen, or etc. is a good problem to have